It is known generally to implement diversity architectures in wireless communications devices to reduce signal fading. WO 01/05088 A1 entitled “Controlled Antenna Diversity”, for example, discloses a post selection diversity scheme in wireless transceivers having spatially separated antennas based upon different level comparison techniques. In signal fading environments, the wireless transceiver in WO 01/05088 A1 selects one received signal over other received signals based upon a comparison of the received signal strength (RSS) levels, for example, just before receiving an assigned TDMA time slot. In static environments, the wireless transceiver in WO 01/05088 A1 selects one received signal over other received signals based upon a comparison of phase error estimates.
In other diversity architectures, two signals received by corresponding receiver antennas are processed simultaneously. In these diversity architectures, additional power is required for down-converting and base band processing the signal received by the parallel diversity branch. One analysis suggests that the addition of a receive diversity branch in wireless receivers increases power consumption by 15% or more.
It is known generally to reduce power consumption in a diversity receiver by selectively enabling a diversity branch in the receiver. WO 01/05088 A1 entitled “Controlled Antenna Diversity”, for example, discloses enabling a diversity branch in a wireless receiver based on local or global criteria only when performance gains from diversity mode operation outweigh the corresponding increase in power consumption attending diversity mode operation. The local criteria disclosed in WO 01/05088 A1 includes measured signal to interference ratio (SIR), estimated bit error rate (BER) or frame error rate (FER), and the number of re-transmissions. The global criteria in WO 01/05088 A1 are based upon monitoring loads on various cells in the communications network for excess capacity. Cells with excess capacity may direct mobile stations to operate without diversity to reduce power consumption in the wireless receiver. In WO 01/05088 A1, networks with excess capacity may offset performance loss by mobile stations directed to operate without diversity by increasing transmission power to the mobile station.
The various aspects, features and advantages of the disclosure will become more fully apparent to those having ordinary skill in the art upon careful consideration of the following Detailed Description thereof with the accompanying drawings described below.